1. Technical Field
The present invention relates to medical therapy systems in general, including therapeutic cooling, heating, and compression systems used in association therewith, and more particularly, but not by way of limitation, to a programmable, thermal therapy and external pneumatic compression for the prevention of deep vein thrombosis.
2. Description of the Related Art
Considerable medical attention has been given to the serious medical issue of Deep Vein Thrombosis (“DVT”). One approach to the prevention of DVT has been External Pneumatic Compressions (“EPC”). EPC has been shown to be helpful as a prophylaxis for DVT, although refinements over existing systems are still in need. For example, multiple articles have been written addressing this issue, including a compilation of recommendations for preventing DVT (Heit J A: Current Recommendations for Prevention of Deep Venous Thrombosis. In: Handbook of Venous Disorders. Gloviczki P, Yao J S, eds. Cambridge, The University Press, 1996). Engineering studies are presented which also address EPC as a preventative for DVT (Kamm R D: Bioengineering Studies of Periodic External Compression as Prophylaxis Against Deep Vein Thrombosis—Part 1: Numerical Studies. J Biomech Engineering 104(1): 87-95, 1982). Such efforts are meritorious for patient health due to possible Pulmonary Embolism (“PE”) resulting from DVT (National Institutes of Health Consensus Development Conference Statement: Prevention of Venous Thrombosis and Pulmonary Embolism. JAMA 6(2) 744-749, 1986). Additionally, studies have been performed relative to DVT and orthopedic surgery (“OS”) (Westrich G H, Sculco T P: Prophylaxis Against Deep Vein Thrombosis After Total Knee Arthroplasty. J Bone Joint Surg 78-A(6): 826-834, 1996).
Relative to OS, physicians have long recognized the need to provide warmth and cooling directly to patients as part of OS therapy. Better recoveries have been reported, for example, using cold therapy for orthopedic patients. The benefits of warming patients undergoing surgery has also been demonstrated. It may also be desirable to cool portions of a patient's anatomy in certain circumstances. Yet another advantageous therapy is the application of heat then cold to certain injured areas. See, for example, U.S. Pat. No. 5,989,285 (the '285 Patent) assigned to Thermotek, Inc. and incorporated herein by reference.
Several devices have been developed that deliver temperature-controlled fluids through pads or convective thermal blankets to achieve the above thermal purpose. Typically these devices have a heating or a cooling element, a source for the fluid, a pump for forcing the fluid through the pad or blanket, and a thermal interface between the patient and the temperature-controlled fluid. U.S. Pat. No. 4,884,304 to Elkins is directed to a mattress-cover device that contains liquid flow channels that provide the selective heating or cooling by conduction.
Devices have also been developed for providing heat to a person in bed. Electric blankets containing electric heating elements have been used for years to warm a person in bed. Cooling blankets, such as the blanket disclosed in U.S. Pat. No. 4,660,388 to Greene, have also been proposed. Greene discloses a cooling cover having an inflatable pad with plenum chambers at opposite ends thereof. Cool gas is generated in a separate unit and directed to the pad and out a number of apertures on the underside of the pad and against the body of the person using the cover.
A disposable heating or cooling blanket that has three layers of flexible sheeting is disclosed in U.S. Pat. No. 5,125,238 to Ragan, et al. Two of the layers form an gas chamber and the third includes a comfortable layer for contact with the patient. Conditioned gas is directed toward the covered person through a multiplicity of orifices in the bottom layers of the blanket.
The temperature-controlled blanket and bedding assembly disclosed in the '285 Patent includes a temperature-controlled blanket and temperature-controlled bedding system that provide both recirculating temperature-controlled fluid and temperature-controlled gas to enhance performance for convectively heating or cooling a patient. Counter-flow or co-flow heat-exchanging principles between the temperature-controlled liquid and the temperature-controlled gas achieve temperature uniformity across different sections of the blanket and the bedding system. Drapes and the temperature-controlled bedding system provide a temperature-controlled envelope around a person using the bedding system. In one embodiment of the bedding system, an gas portion of the bedding system is provided that supplies a fluid portion of the overall bedding system. In another embodiment of the bedding system, the fluid portion of the bedding system is provided for use with a patient bed that supplies the gas portion of the overall bedding system.
U.S. Pat. No. 5,097,829 to Quisenberry describes an improved temperature-controlled fluid-circulating system for automatically cooling a temperature-controlled fluid in a thermal blanket with a thermoelectric-cooling device having a cold side and a hot side when powered by electricity. The temperature-controlled fluid is cooled by a cold side of the cooling device and is pumped through, to, and from the blanket through first and second conduits.